Latino preschool children have higher rates of overweight and obesity compared with children in other racial/ethnic groups. Few family-based obesity interventions exist that focus on Latino preschool children and use culturally-appropriate measures and approaches. Latino peer health educators (promotoras) can be effective in increasing knowledge and promoting behavior change in Latino populations; however, to date, no promotora-mediated child obesity interventions targeting Latino preschool children exist. The purpose of the proposed research is to develop and evaluate the feasibility and effectiveness of a family-based, promotora-mediated child obesity intervention. The proposed study will employ a mixed methods sequential research design, organized into two major phases: Phase I: Conduct formative research (focus groups and cognitive interviews with Latino parents of preschool children) to inform the development of a culturally-appropriate intervention and measures; Phase II: Test the feasibility and effectiveness of a promotora-mediated, family-based intervention to prevent obesity in Latino preschool children; Thirty Latino parents of children aged 2-5 years (Phase I) and fifty parent-child dyads (Phase II) will be recruited from Newberry and Saluda counties, South Carolina by promotoras from within their own social networks (e.g., neighborhood, church, school, corner stores). Promotoras will receive 20 hours of training using the intervention curriculum developed in Phase I and then deliver the intervention to families over 10 weekly home sessions. The intervention will educate and train parents to set feasible goals related to family diet, physical activity, and sedentary activity to create supportive home environments to promote a healthy weight in their children. Primary outcomes (i.e., child body mass index (BMI) z-score and percentile) and secondary outcomes (i.e., child waist circumference, diet, and physical activity, parent BMI and waist-to-hip ratio, te physical and social home environment, and demographics) will be assessed pre- and post-intervention. Process evaluation will assess fidelity, dose, reach, recruitment, and contextual factors using multiple data sources and mixed methods. Descriptive analyses based on data collected from the promotoras and parents in the process evaluation protocol will be used to determine intervention feasibility and level of implementation. Intervention impact on primary and secondary outcomes controlling for relevant variables will be assessed with ANCOVA in SAS. The proposed research carries high public health significance because it will influence specific behaviors in parents and children that have been shown to contribute to excessive weight gain. The research is innovative because it will be the first to use promotoras in a child obesity intervention for Latino preschool- age children. If successful, this approach will be evaluated in a large-scale intervention study and provide a potential model to help to address and prevent obesity in Latino families with young children.